It is known practice to use circuit-breakers, which respectively protect downstream loads, in power distribution installations. In order to retrieve data points (operating data) of the switches, the latter are connected to a test device (generally: a correspondingly suitable device) via a data connection. In this case, the switch is used as the data source and the test device is used as the data sink. In order to retrieve data points of the switch, the data points must be known to the test device. Firmware updates often result in the switches having new functionalities and thus new data points. If a new data point of the switch is not known to the test device, the latter can neither retrieve nor use the data point. Consequently, the retrieval of a new data point must be preceded by its disclosure. This may be effected, for example, by way of a firmware update of the test device.